1. Field of the Invention
The present invention relates generally to web handling, and more particularly to a web cinching and winding apparatus and method. To cinch the web end portion onto a core, the core is center driven at an outer peripheral speed greater than the transport speed of the web end portion to be threaded around the core. After the web end portion is cinched onto the core and the web wound to form a roll of predetermined diameter, the core center drive is terminated, and substantially simultaneously the outer surface of the roll is surface driven.
2. Description of the Prior Art
U.S. Pat. No. 3,585,779 discloses a winding apparatus in which a web end portion is cinched onto a spool by rotatably driving the spool at an outer peripheral speed in excess of the speed at which the web end portion is threaded around the spool. After cinching, the web is wound onto the spool by continued driving of the spool, commonly referred to in the industry as center drive winding.
It is also known in the prior art, of which U.S. Pat. Nos. 3,537,664 and 3,692,252 are exemplary, to initially attach or fasten a web end portion onto a core, and then drive the outer surface of web convolutions on the core by means of a builder roller to form a roll. This means of winding a roll is commonly referred to in the industry as surface winding.
A web cinching device is disclosed in U.S. Pat. No. 3,884,427 wherein web cinching is achieved by an endless belt wrapper. A wrapping mechanism wraps a belt almost completely around the outer periphery of a core leaving a small gap between the belt and core into which a web end portion is fed. After the web end portion is cinched onto the core, the belt is withdrawn.
One of the problems with the center driven winding device is adequately controlling winding torque and web tension as the roll diameter increases, particularly where large rolls are wound. This has in instances necessitated the use of complicated and expensive control devices.
In surface driven winding devices, the web and core are traveling at the same speed. Since cinching a web end portion on a core can be defined as tightening a web by pulling on the web while holding the core (after the web end portion has entered the nip between the core and first web convolution) relative motion between the web and core is implied. Since relative motion between the web and core is not present in surface winding, cinching as defined above is unobtainable. In order to attach the web end portion to the core, means must be provided such as closely spaced threading guides, rollers or elastic bands surrounding the core to insure intimate contact of the web to the core. Such threading guides present problems, for example, of increased costs and reduced reliability due, among other things, to the precision required in manufacturing the parts, and the close tolerances involved in assembly and operation.
A problem with belt or band wrapping devices is difficulty of adjusting the device which is extremely critical. Improper adjustment of the belt wrapping device can result in web surface abrasion when the belts are around the core, and cinching failures with severe consequences. The belts further have to be replaced periodically.